PCR typing of Plasmodium falciparum in matched peripheral, placental and umbilical cord blood

A study was carried out in Lambarene, Gabon, to analyse malarial infections in pregnant women. Blood samples from peripheral circulation and term placentas from 37 women were diagnosed as parasite-positive by thick blood smears. Infection was confirmed by PCR, using single-copy merozoite surface protein 1 and 2 genes. Of the 37 matched cord blood samples, 17 were positive by PCR amplification, even though all but one were microscopically negative. Five of these 17 samples were verified as positive in an antigen detection assay for histidine-rich protein 2. A comparison of alleles from these compartments indicates that single clonal infections were predominant for the cord samples, while double and triple infections were more common for peripheral and placental samples. Knowledge of the occurrence of parasites in each blood sample type is important towards understanding population dynamics in pregnant women and the development of immunity in infants to selected genotypes.